Cobalt is one of the most significant supply chain risks threatening widespread adoption of electric cars, trucks and other electronic devices requiring batteries. This mineral, which is especially well suited for the purpose of stabilizing lithium-ion battery cathodes, is mined almost exclusively in the Democratic Republic of Congo under abusive and inhumane conditions.
Electric vehicle manufacturers are eager to curtail the use of cobalt in their battery packs in order to reduce costs as well as to counter the child labor practices used to mine the mineral. Research has also shown that cobalt can lead to oxygen release at high voltage, causing damage to lithium-ion batteries. All of these concerns make it desirable to find alternatives.
One alternative is the use of nickel-based cathodes. However, these come with their own problems, such as poor heat tolerance, which can lead to oxidation of battery materials, thermal runaway and even explosion. And while high-nickel cathodes accommodate larger capacities, volume strain from repeated expansion and contraction can result in poor stability and safety concerns.
As a result, researchers have sought to address these issues through compositionally complex high-entropy doping using so-called HE-LMNO. This involves using an amalgamation of the "transition metals" magnesium, titanium, manganese, molybdenum and niobium in the structure's interior, with a subset of these minerals used on its surface.
As explained recently in Nature, the researchers demonstrated that their new HE-LMNO zero-cobalt cathode exhibited an unprecedented volumetric change of zero during repeated use. This highly stable structure is capable of withstanding more than 1,000 cycles and high temperatures, which makes it comparable to cathodes with much lower nickel content.
This research could set the stage for the development of an energy-dense alternative to existing batteries.